The answer is to use memory-optimized instances like r5.xlarge for the core nodes. This is correct because when CloudWatch shows CPU utilization below 20% but memory near 90%, it indicates the data is spilling to disk due to insufficient RAM, which dramatically slows Spark jobs. Memory-optimized instances provide more memory per core, allowing the dataset to fit in memory and avoiding costly disk spills. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your ability to diagnose resource bottlenecks in EMR Spark workloads—a common trap is assuming more nodes (scaling out) will help, but the real fix is scaling up memory per node. Remember the memory tip: when CPU is low but memory is high, think “spill to disk, r5 is your risk.”
DEA-C01 Data Operations and Support Practice Question
This DEA-C01 practice question tests your understanding of data operations and support. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A data engineer is running an Amazon EMR cluster with Spark to process log files. The cluster uses instance fleets with m5.xlarge core nodes. The engineer observes that the Spark job is running slower than expected. CloudWatch metrics show that the cluster's CPU utilization is below 20% but memory utilization is near 90%. Which configuration change would most likely improve performance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use memory-optimized instances (r5.xlarge) for core nodes.
Option D is correct because high memory usage with low CPU indicates that the data does not fit in memory, causing spills to disk. Using a memory-optimized instance type (e.g., r5.xlarge) provides more memory per core. Option A is wrong because increasing core nodes adds more CPU but does not address memory per node. Option B is wrong because reducing nodes reduces total memory. Option C is wrong because the issue is memory, not shuffle partitions.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Use memory-optimized instances (r5.xlarge) for core nodes.
Why this is correct
r5 instances have higher memory-to-CPU ratio, reducing memory pressure and spills.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the number of core nodes from 5 to 10.
Why it's wrong here
Adding more nodes adds CPU and memory, but the memory per node remains the same, and the job may still spill.
✗
Increase the number of Spark shuffle partitions.
Why it's wrong here
Shuffle partitions affect parallelism but not memory usage per task.
✗
Decrease the number of core nodes to reduce overhead.
Why it's wrong here
Reducing nodes reduces total memory, worsening the problem.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Data Operations and Support — This question tests Data Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use memory-optimized instances (r5.xlarge) for core nodes. — Option D is correct because high memory usage with low CPU indicates that the data does not fit in memory, causing spills to disk. Using a memory-optimized instance type (e.g., r5.xlarge) provides more memory per core. Option A is wrong because increasing core nodes adds more CPU but does not address memory per node. Option B is wrong because reducing nodes reduces total memory. Option C is wrong because the issue is memory, not shuffle partitions.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.